Cyber Monday ... expected to be the biggest online shopping day of the year.

The Cyber Monday crackdown comes on what's expected to be the biggest online shopping day of the year. US Immigration and Customs Enforcement's Homeland Security Investigations co-ordinated the effort with Europol and police in Belgium, Denmark, France, Romania and the United Kingdom.

Authorities say it's the third consecutive Cyber Monday that websites selling knock-off sports jerseys, DVDs and other goods have been targeted.